The embodiments described herein relate generally to methods and system for treating sour water and, more particularly, to methods and system for use in removing contaminates from sour water.
At least some known systems, such as gasification systems, produce sour water. As used herein, the term “sour water” refers to water that includes cyanide, hydrocarbons, hydrogen sulfide, ammonia, phenol, selenium, salts, organics, and/or other chemicals. Further, as used herein, the term “cyanide” refers to any chemical compound that includes a carbon atom bonded to a nitrogen atom (CN), such as simple cyanides and/or cyano complexes, the term “ammonia” refers to any chemical compound that includes NH3 and/or NH4OH, and the term “organics” refers to any chemical compound that includes carbon (C). Further, as used herein, the term “contaminates” refers to cyanide, ammonia, and/or organics.
In at least one known gasification system, a low temperature gas cooling section produces sour water in the form of recovered process condensate. A condensate ammonia stripper removes ammonia, hydrogen sulfide (H2S) and/or other trace components from the recovered process condensate to produce stripped sour water. Cyanide from the stripped sour water may become concentrated in an overhead reflux stream within a column downstream from the condensate ammonia stripper. In such a system, a small blowdown stream, i.e., approximately 1-10 gallons per minute (gpm), of sour water is routed from the reflux stream to a recycle solids tank for use in preventing cyanide from concentrating in the column and/or overhead piping. Without the blowdown stream, high metallurgy materials may be required in a reflux pump suction, a reflux pump, an overhead condenser, and/or condenser return piping to the overhead condenser. When routed to the recycled solids tank and/or pumped to a grinding mill, cyanide from the blowdown stream can potentially create exposure hazards.
As such, it is desirable to remove contaminates from sour water before the sour water is channeled to a recycle solids tank and/or a grinding mill. More particularly, it is desirable to remove contaminates from sour water streams produced in an ammonia stripping system of a gasification system.